Balancing means for a rotating speaker system

ABSTRACT

A rotating speaker system comprising a rotating cylindrical housing having a speaker therein on one side of the axis of rotation and an adjustable counterbalance on the opposite side of the axis of rotation externally adjustable for both static and dynamic balance.

United States Patent 1 1 1111 3,797,606

Edwards Mar. 19, 1974 1 BALANCING MEANS FOR A ROTATING 3.058.541 10/1962 Leslie 181/27 A SPEAKER SYSTEM 3,070,660 12/1962 lppolito 179/1 J {75] Inventor: John W. Edwards, Lake Zurich, Ill. [73] Assignee: Hammond Corporation, Deerfield,

Ill.

[22] Filed: Feb. 12, 1973 [21] Appl. No.: 331,686

[52] U.S. Cl. 181/27 A, 181/31 B, 179/1 J [51] Int. Cl. H04r l/28, GlOk 13/00 [58] Field of Search 181/27 A, 31 B; 179/1 J; 84/ 1.25

[56] References Cited UNITED STATES PATENTS 2,831,051 4/1958 Teikowski 179/11 Primary Examiner-Stephen J. Tomsky Attorney, Agent, or Firm-Lowell C. Bergstedt 5 7] ABSTRACT A rotating speaker system comprising a rotating cylindrical housing having a speaker therein on one side of the axis of rotation and an adjustable counterbalance on the opposite side of the axis of rotation externally adjustable for both static and dynamic balance.

8 Claims, 2 Drawing Figures I/I I Pmmmm 1 9 m4 3; 797.606

BALANCING MEANS FOR A ROTATING SPEAKER SYSTEM DESCRIPTION OF THE PRIOR ART In the provision of a tremolo effect for electronic organs, it has been the practice to provide a generally cylindrical speaker housing carrying a speaker in the cylindrical periphery thereof which is mounted to rotate about its axis so as to obtain a rotating projection of the sound. The location of the speaker away from the axis of rotation of the housing results in an unbalanced condition which would shake the instrument, wear the bearings, and eventually generate extraneous noise. It is, therefore, necessary that the speaker be balanced. To this end, it has been the practice to mount a counterweight inside the rotating housing on the opposite side of the axis of rotation from the speaker which is finely adjusted for counterbalancing effect by drilling holes or adding minor weights such as screws, nuts and washers. This procedure is time consuming in itself and presents further difficulty in that the counterweight is bestlocated on the interior of the drum and the drum is preferably closed for acoustical reasons. Therefore, adjustment of the counterweight requires a partial disassembly and reassembly.

SUMMARY OF THE INVENTION This invention contemplates a'counterweight within a rotating drum on the inside wall of the drum opposite the speaker carried thereby. The counterweight is a metal bar oriented parallel to the axis of the drum and mounted within the drum for translational movement toward and away from the axis of the drum and for tilting movement in the plane of bodily movement to com pensate for both static and dynamic imbalance. Externally adjustable means extend through the wall of the drum and bear against the counterweight to effect both the translational and tilting movement.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a tremolo unit embodying the present invention; and

FIG. 2 is an enlarged central section through the unit of FIG. l taken along the line 22 of FIG. 1 looking in the direction of the arrows.

DESCRIPTION OF A PREFERRED EMBODIMENT As shown in FIGS. 1 and 2, the tremolo unit comprises a drum-shaped assembly consisting of a top disc 12 and a bottom disc 14 on opposite sides of a cylindrical side wall 16. These parts are formed of hardboard, the top and bottom discs being glued and nailed to the edges of the cylindrical wall 16. The ends of the hardboard forming the cylindrical wall 16 are concavely cut to define together a speaker opening 18. These ends are secured to the mounting flange 20 of a speaker 22 to maintain the cylindrical form of the wall 16. A transversely split axle 24 consisting of shafts 24a and 24b extends through the axis of the housing 10 and is contained in the top and bottom discs by rubber grommets 26 which engage the shafts tightly. The inside race of bearings 28 ride against the grommets 26, the outside races thereof being mounted to support the drum for rotation. A pulley 30 is affixed to the lower protruding end of the shaft 24b for driving the tremolo unit. Within the housing, an insulating sleeve 32 telescopes over the facing ends of the split axle 24 and 2 screws 34 extend through the sleeve 32 and into the ends of shafts 24a and 24b to position the shafts a short distance apart in insulated relation with respect to each other. The speaker leads 36 are mounted to the screws 34. Contact elements 38 bear against the ends of the shafts to deliver the signal to the speaker 22.

The counterbalance assembly 40 is situated within the housing oppositely from the speaker 22. A T-nut 42 is mounted centrally in the cylindrical wall 16 of the housing between the top and bottom discs 12 and 14. A stud 44 is screwed into the T-nut to extend toward the axis of the housing. An elongated metal counterweight plate 46 having a central hole 48 therein appreciably larger than the stud 44 is fitted loosely on the stud. The length of the plate should approach relatively closely the top and bottom discs 12 and 14 so as to prevent the plate from turning on the stud away from its intended location of the major axis thereof extending perpendicularly to the discs 12 and 14. The plate is held on the stud 44 by a speed nut 50 and a spring 52 between the speed nut and the plate 46. The spring is of relatively large diameter so as to have a substantial area of bearing on the plate and desirably has ground, plane parallel ends perpendicular to the axis of the spring.

A pair of screws 54 are threaded into the cylindrical wall 16 above and below the T-nut 42 into contact with the plate 46. Sheet metal screws lend themselves admirably to this purpose in that, with their hardened ends, they dig slightly into the metal plate 46 and play a position-retentive function with respect to the plate as well as an adjustment function.

The adjustment procedure will be readily understood from the foregoing description. The screws 54 are turned in or out to move the plate 46 bodily toward or from the axis of rotation of the assembly to balance the weight of the speaker and arrive at a static balanced condition. Dynamic imbalance is, of course, determined by rotating the assembly, and any imbalance found is corrected by adjusting the screws individually so as to move one end of the plate or the other nearer the axis of rotation.

The plate is not prone to shake or vibrate away from its intended position. The large bearing of the spring 52 on the plate with the accurately formed ends of the spring prevent a rolling of the plate about its vertical axis. The screws 54 in combination with the spring 52 positively locate the plate in reference to its horizontal axis. As to the plate turning on the stud 44, as stated before, the close approach of the ends of the plate to the top and bottom discs puts positive limits to such movement. In addition, however, the sharp points of the screws 54 indent slightly thesurface of the plate and the pressure of the spring 52 makes it dificult for the indentations to escape the screw points.

As an illustration of the dimension of the counterweight, a 6 X 9 elliptical speaker is well suited to the production of the desired tremolo. To counterbalance this speaker a steel plate 8 X 3 X 0.179 has been successfully employed.

1 claim:

1. A counterbalance for a rotating speaker system which includes an enclosure having a peripheral wall, end walls, means associated centrally with said end walls for supporting said enclosure for rotation and de- I member, means mounting said member within said enclosure opposite said speaker for bodily translation toward and away from said axis and for pivotal movement on an axis in a plane normal to said axis of rotation to vary the angle between the axis of said member extending between said end walls and said axis of rotation and externally operable means for effecting said translation and said angular variation.

2. The combination of claim 1 wherein said mounting means includes means resiliently urging said member outward and said externally operable means positively oppose said resilient means.

3. The combination of claim 1 wherein said mounting means includes a spring in compression urging said member outward and said externally operable means engage the face of said member opposite that against which said spring bears and on opposite sides of said spring.

4. The combination of claim 3 wherein said externally operable means comprise threaded members engaged in said peripheral wall and bearing against said face of said counterbalancing member.

5. The combination of claim 1 wherein said member is a plate having a central hole therethrough, said mounting means comprises a post mounted in said peripheral wall and extending toward said axis through said hole and a spring contained in compression beancing member, means mounting said member inside said enclosure away from said axis oppositely to said speaker, said mounting means including externally operable means for moving said member toward and away from the axis of rotation.

7. The combination of claim 6 wherein said mounting means includes means resiliently urging said member outward and said externally operable means positively oppose said resilient means.

8. The combination of claim 6 wherein said mounting means includes a spring in compression urging said member outward and said externally operable means engage the face of said member opposite to that engaged by said spring and on opposite sides of said spring in a line parallel to said axis. 

1. A counterbalance for a rotating speaker system which includes an enclosure having a peripheral wall, end walls, means associated centrally with said end walls for supporting said enclosure for rotation and defining an axis of rotation, and a speaker mounted in said peripheral wall; comprising a counterbalancing member, means mounting said member within said enclosure opposite said speaker for bodily translation toward and away from said axis and for pivotal movement on an axis in a plane normal to said axis of rotation to vary the angle between the axis of said member extending between said end walls and said axis of rotation and externally operable means for effecting said translation and said angular variation.
 2. The combination of claim 1 wherein said mounting means includes means resiliently urging said member outward and said externally operable means positively Oppose said resilient means.
 3. The combination of claim 1 wherein said mounting means includes a spring in compression urging said member outward and said externally operable means engage the face of said member opposite that against which said spring bears and on opposite sides of said spring.
 4. The combination of claim 3 wherein said externally operable means comprise threaded members engaged in said peripheral wall and bearing against said face of said counterbalancing member.
 5. The combination of claim 1 wherein said member is a plate having a central hole therethrough, said mounting means comprises a post mounted in said peripheral wall and extending toward said axis through said hole and a spring contained in compression between the inner end of said post and said plate, and said externally operable means comprise a pair of screws threaded in said peripheral wall on opposite sides of said post and bearing against said plate.
 6. A counterbalance for a rotating speaker system which includes an enclosure, means for mounting said enclosure for rotation and defining an axis of rotation therefor, and a speaker mounted on one side of said enclosure away from said axis; comprising a counterbalancing member, means mounting said member inside said enclosure away from said axis oppositely to said speaker, said mounting means including externally operable means for moving said member toward and away from the axis of rotation.
 7. The combination of claim 6 wherein said mounting means includes means resiliently urging said member outward and said externally operable means positively oppose said resilient means.
 8. The combination of claim 6 wherein said mounting means includes a spring in compression urging said member outward and said externally operable means engage the face of said member opposite to that engaged by said spring and on opposite sides of said spring in a line parallel to said axis. 